In human fear conditioning 'resistance to extinction' occurs when the removal of the aversive outcome fails to produce a reduction in conditioned responding. This phenomenon is important to understanding the persistence of anxiety disorders such as phobias. The research presented in this thesis examines factors that promote the acquisition and maintenance of learned fear response and attempts to differentiate between different explanations of the resistance to extinction phenomenon. To investigate the impact of different conditioning procedures (evaluative or classical conditioning) on the durability of the conditioned response (CR), event-related potential (ERP) methodology was employed. In addition, the role of the fear-relevance of the conditioned stimulus (CS), in supporting the acquisition and resistance to extinction of the CR, was explored. Evidence suggested that extinction effects are likely to reflect procedural differences in conditioning rather than different underlying learning processes. Extinction effects were dissociable across procedures, supporting the role of the type of unconditioned stimulus (US) in explaining past demonstrations of extinction when responses were indexed by physiological measures. Verbally transmitted, threat information heightened aversive US-expectancies and fear beliefs without the need for conditioning. Additionally, fear-beliefs were reduced without the need for extinction training when positive information was provided. Contrary to Davey's (1997) expectancy bias model, the results do not support the hypothesis that verbal information interacts with direct contingency experience to create fear responses; instead, information appears to be a direct pathway to fear. ERP measures for fear responses did not echo the effects of verbal information and contingency on fear-beliefs. However, the comparability of our ERP data, to other research using physiological measures of response, is discussed regarding the number of trials required to calculate the average ERP response. Due to averaging over a large number of trials the ERP measure may not be sensitive to fluctuations in response that may be dependent on information or contingency manipulations. In conclusion our data suggests the importance of verbal information as a pathway to fear and the role of cognitive factors in the prevention and treatment of fears.